Tobias Kamp

Catenary trucks are the key to accelerating the electrification of freight transport on highways and to reduce carbon emissions. This article introduces a 200 kW, highly efficient, highly compact, galvanically isolated, and bidirectional on-board charger that interfaces the dc overhead lines with the traction battery. By means of a flexible modularization and control technique, both 600 V and 1.2 kV are compatible catenary voltages. The chosen dc-dc converter topology is the three-phase dual-active bridge, which achieves a full-load efficiency of 98.5 % and a volumetric power density of 6.48 kW/dm3. Key enablers to accomplishing this volumetric power density are modern 1.2 kV silicon carbide semiconductor devices and highly compact 3D-printed fluid coolers. In addition to characterizing the steady-state efficiency, the experiments also validate the closed-loop control algorithms. This highly efficient and compact prototype is a milestone for the commercialization of catenary trucks.

Monitoring or estimating the junction temperature of power semiconductor devices is a requirement for degradation monitoring and predictive maintenance of power-electronic converters and usually achieved by online measurement of a temperature-sensitive electrical parameter (TSEP). Many TSEPs rely on switching transients and thus depend on the design of a switching cell, driving significant calibration efforts. Instead, utilizing the on-state voltage of a power semiconductor device as TSEP is attractive, as it only depends on the load current and the output characteristic of the device. This independence of the switching cell design enables on-state voltage monitoring circuits to be seamlessly integrated into products that are already mass-produced. However, an effective on-state voltage monitoring circuit has to measure small on-state voltages accurately and fast while withstanding high off-state voltages. This article experimentally evaluates three candidate circuits that take on this challenge: a circuit derived from a Wheatstone bridge, a dynamically compensated voltage divider and a circuit using an auxiliary MOSFET. PCBs are designed, featuring all three circuit concepts, and experiments are carried out to compare the candidate circuits in terms of dynamic performance and resolution. Finally, the potential for integration into commercial products is outlined, illustrated, and discussed.